Use JSON.stringify() to wrap your json
var parameter = JSON.stringify({type:"user", username:user_email, password:user_password});
$http.post(url, parameter).
success(function(data, status, headers, config) {
// this callback will be called asynchronously
// when the response is available
console.log(data);
}).
error(function(data, status, headers, config) {
// called asynchronously if an error occurs
// or server returns response with an error status.
});